Laboratory-prepared magnesium silicate (MgSi-I) was modified with HNO3, H3PO4 and NaOH to give MgSi-II, -III and -IV, respectively. The modified products were examined in respect to structure, thermal stability and ion exchange properties. The investigations indicated that MgSi-I has strong tendency to react with alkaline and acid media, especially with the phosphate group. The sorption performance of the materials for Cu2+, Cd2+, Ni2+ and Fe3+ transition metal ions was studied as a function of pH. The modified materials offer excellent potential for heavy metals removal compared to the unmodified one. Magnesium silicate that treated with HNO3 (MgSi-II) revealed the higher silica content, thermal stability and sorption efficiency relative to the other series. Besides, it retains 62.8% of its ion exchange capacity after heating up to 400 degrees C. (C) 2010 Elsevier B.V. All rights reserved.